1. Field of the Invention
The present invention relates to a novel polyester and a production process thereof. Specifically, it relates to a polyester having high heat resistance, low water absorbency, low optical anisotropy, and satisfactory formability (moldability), and to a production process of the polyester. The polyester is useful as, for example, an optical material, electronic information material and medical device material.
2. Description of the Related Art
Intensive investigations have been made for the application of plastics to optical materials, electronic information materials and medical device materials. Such plastics for use as optical materials or electronic information materials must have low optical anisotropy in addition to high transparency, low water absorbency and high heat resistance. Likewise, plastics for use as medical device materials must have high compatibility with blood, high mechanical strength and sufficient resistance to hydrolysis.
Polymethyl methacrylates, polycarbonates and amorphous polyolefins are used as the optical materials. However, the polymethyl methacrylates have high hygroscopicity to cause deformation such as warpage and have insufficient heat resistance, although they have excellent transparency and low optical anisotropy. The polycarbonates are high in optical anisotropy, although they are excellent in heat resistance. The amorphous polyolefins are insufficient in formability (moldability) and adhesive property, although they are low in optical anisotropy and are excellent in heat resistance.
Separately, attempts have been made to use polyesters as optical materials or electronic information materials. For example, Japanese Unexamined Patent Application Publication No. 1-138225 discloses a polyester resin obtained by using a diol or dicarboxylic acid having an aromatic ring in a side chain. Japanese Unexamined Patent Application Publication No. 2-38428 discloses a polyester copolymer obtained by using diphenyldicarboxylic acid as a dicarboxylic acid component. Japanese Unexamined Patent Application Publication No. 11-35665 discloses a polyester including a 2,2-norbornanedimethanol derivative, terephthalic acid, and other components. However, these resins do not always have high heat resistance, low water absorbency and satisfactory optical characteristics.
Polyesters each having an adamantane skeleton are also known. For example, Japanese Examined Patent Application Publication No. 46-34628 discloses a process for producing a linear polyester, in which a diol component containing adamantanediol is allowed to react with a dicarboxylic anhydride component containing an unsaturated carboxylic anhydride. However, the resulting resin obtained by this process is insufficient in heat resistance and transparency, although it can have stability against hydrolysis and against solvent by action of curing. Japanese Unexamined Patent Application Publication No. 50-21090 discloses a process for producing a polyester by polycondensation of a dihydroxyadamantane with an aromatic dicarboxylic acid. However, the resulting polyester does not always have sufficiently low water absorbency and excellent optical characteristics, although it has excellent formability.
Accordingly, an object of the present invention is to provide a novel polyester that has high heat resistance, low water absorbency, satisfactory optical characteristics and excellent formability, and to provide a production process of the polyester.
After intensive investigations to achieve the above objects, the present inventors have found that a polyester resin having a specific structure has high heat resistance, low water absorbency, satisfactory optical characteristics and excellent formability (moldability). The present invention has been accomplished based on these findings.
Specifically, the present invention provides, in one aspect, a polyester that is a polycondensation product of a diol component (i) and a dicarboxylic acid component (ii). In the polyester, the diol component (i) includes a tricyclo[3.3.1.13,7]decanediol represented by following Formula (1): 
wherein n is 0 or a positive integer, and carbon atoms constituting a ring may each have a substituent; or the dicarboxylic acid component (ii) includes a tricyclo[3.3.1.13,7]decanedicarboxylic acid represented by following Formula (2): 
wherein m is 0 or a positive integer, and carbon atoms constituting a ring may each have a substituent.
The polyester includes, for example, a polyester obtained by polycondensation of the diol component (i) containing the tricyclo[3.3.1.13,7]decanediol of Formula (1) and the dicarboxylic acid component (ii) containing the tricyclo[3.3.1.13,7]decanedicarboxylic acid of Formula (2).
In another aspect, the present invention provides a process for producing a polyester. The process includes the step of subjecting a diol component (i) to polycondensation with a dicarboxylic acid component (ii) or a reactive derivative thereof, in which a diol component including the tricyclo[3.3.1.13,7]decanediol of Formula (1) is used as the diol component (i), or a dicarboxylic acid component including the tricyclo[3.3.1.13,7]decanedicarboxylic acid of Formula (2) is used as the dicarboxylic acid component (ii).
Preferably in this production process, a diol component containing the tricyclo[3.3.1.13,7]decanediol of Formula (1) as the diol component (i) is subjected to polycondensation with a dicarboxylic acid component, or a reactive derivative thereof, including the tricyclo[3.3.1.13,7]decanedicarboxylic acid of Formula (2) as the dicarboxylic acid component (ii).
As the diol component (i), a diol component containing a tricyclo[3.3.1.13,7]decanediol represented by following Formula (1a): 
wherein carbon atoms constituting a ring may each have a substituent, can be used. As the dicarboxylic acid component (ii), a dicarboxylic acid component containing a tricyclo[3.3.1.13,7]decanedicarboxylic acid represented by following Formula (2a): 
wherein carbon atoms constituting a ring may each have a substituent, can be used.
The polyester of the present invention has a bulky alicyclic structure and has high heat resistance, low water absorbency, satisfactory optical characteristics, and excellent formability. Accordingly, the polyester is useful as a material for an optical disk, lens, optical connector, and other optical-electronic information devices, as well as a material for a transfusion solution kit, catheter, syringe, vacuum blood collecting tube, and other medical devices.